Device for welding tubular components of plastics material

ABSTRACT

A device for manufacturing a welded connection of tubular components of plastics material. The ends of the components to be connected are axially aligned and held to abut with the end surfaces. The ends of the tubular components can be heated by a foldable heating device which surrounds the tubular components. A support device is arranged in the interior of the tubular components. A heating device which can be fastened on a frame in a determined position is provided for each pipe diameter dimensioned to be welded. Electrical contacts are provided for each heating device. A welding program of a program control predetermined for each dimension can be selected by the contacts when the heating device is placed on the frame.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a device for welding tubular components ofplastics material, as characterized in the preamble of claim 1.

A device for welding tubular components is known in which the heatablejaws have at the inner circumference an annular duct in which a vacuumis generated during or after the welding process of the axially abuttingtubular components. The vacuum has the purpose to prevent the moltenmaterial to drop inwardly or to prevent the formation of an inner beadat the welded connection. However, it has been found that it is notpossible to manufacture welded connections by means of this method andby means of this device which are of sufficient strength and smooth atthe inner circumference.

It is also known (DE-PS 283 0722), for reducing inner welding beads atthe circumference of the tubular components, to arrange an elasticinsert which presses against the inner welding bead.

However, for welding the tubular components, the ends thereof are heatedby pressing them against heating elements and the ends are subsequentlypressed together. A welded connection which is completely free of beadscannot be achieved by means of this method. In addition, by heating thefront ends of the tubular components, the interior of these componentsmay be contaminated, so that the necessary cleanliness is not achievedand the connection is not suitable for pipeline systems which conductmedia having a high degree of purity.

A device of the above-mentioned type is known from DE-C2 29 23 205 bymeans of which welding of the ends of tubular plastic components whichis free of beads is possible.

This device can only be used for one pipe dimension. The heating devicehas half shells of metal the middle portion of which is electricallyheatable for the butt joint and the other portion at both ends seen inlongitudinal direction is equipped with cooling chambers. This requiresa complicated construction and a control of the individual zones whichis very disadvantageous. In addition, the heating zone cannot be quicklycooled after the heating process which results in long welding times.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide a device of theabove-mentioned type by means of which it is possible to manufacture abead-free and secure connection of tubular components of plasticsmaterial, wherein the device must be of simple construction and equippedfor a problem-free operation even if used at the place of assembly of apipeline system which is particularly intended for the conduction ofmedia having a high degree of purity. In addition, it should be possibleto use the device for welding tubular components having differentdiameters, while requiring short change-over times, short welding timesand always resulting in uniformly excellent welded connections.

In accordance with the invention, the object is met by thecharacterizing features of claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

An example of the invention is illustrated in the enclosed drawings andis described in the following.

In the drawing:

FIG. 1 shows a partial front view of a device for welding,

FIG. 2 shows a section along the line II--II of FIG. 1,

FIG. 3 shows a partial section along line III--III of FIG. 2,

FIG. 4 shows a partial section of a different embodiment of FIG. 2,wherein the section extends transversely through the heating device, and

FIG. 5 shows a sectional view along line V--V of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a partial front view of the device with a frame 1, aheating device 2 and a pipe clamping device 3, wherein on the secondside of the heating device 2 is provided another pipe clamping device,not shown.

As can be seen in FIG. 2, guides 4a, 4b are arranged on the upper sideof the frame 1. The pipe clamping devices 3 are slidable in longitudinaldirection on the guides 4a, 4b and can be fixedly connected to the frame1 by means of gripping devices 5.

The heating device 2 can be mounted on the guides 4a, 4b and can befixedly connected by means of gripping devices 5, wherein positioning inlongitudinal direction of the guides 4 is provided by a pin 6 arrangedin the frame 1 which pin 6 engages in a corresponding recess 7 of theheating device 3.

As can be seen in FIG. 2, the heating device 2 is composed of a lowerportion 20 with a receiving means 21a of semicircular cross-section forthe tubular components 8 to be welded and an upper portion 22 with acorresponding receiving means 21b. The upper portion 22 is connected tothe lower portion 20 by means of a hinge joint 23 so that the upperportion 22 can be folded up and the upper portion 22 and the lowerportion 20 can be clamped together by means of a clamping device 24.

The clamping device 24 has an eccentric disk 26 which is rotatable bymeans of a turning grip 25. The eccentric disk 26 has an eccentric innerclamping surface 26a which interacts with a clamping bolt 27 of thelower portion 20. As can be seen in FIG. 3, each of the two receivingmeans 21a, 21b has a concentrically arranged electrically heatable jaw28 and holding jaws 29 on both sides of the heatable jaw 28, andsidewalls 30 which are fastened on a housing 20a or 22a of the lowerportion 20 or upper portion 22, respectively.

The holding jaws 29 are of a poorly heat conducting material, such as,for example, a stainless steel and are fastened by means of screws 31and spacer bolts 32 on the side walls 30, wherein the heatable jaw 28 isfixedly held between the holding jaws 29. The jaws 28 are of a materialwith good heat conductivity, such as, for example, copper and have eachan electric heating cartridge 33 or another electric heating device. Theinner walls of the housing 20a, 22a and the side walls 30 form a commonduct 34 which surrounds the heatable jaws 28 and the holding jaws 29.Cooling air which can be generated by means of a ventilator 9 isconducted through the duct 34. The ventilator 9 is arranged directlyunderneath the heating device 2 in the box-shaped frame 1 and can bedriven by means of an electric motor 10 (see FIGS. 1 and 2).

The side walls 30 have at the inner circumference a recess 35 which inshape and size corresponds to the beads on the tubular components 8which ar to be welded together and are constructed as fittings. As aresult, the fittings are held in the correct position in axialdirection.

Each of the diameter dimensions of the tubular components to be weldedtogether has its own heating device 2 which is placed on the frame. Theheating device 2 is preferably constructed for the standard diameters16, 20, 25, 32, 40, 50 and 65 mm. An electric switch 11 is provided onthe frame 1 for each of the heating devices 2. The switches 11 arearranged next to each other in longitudinal direction of the guides 4.

When the heating device 2 for a certain diameter dimension is mounted, apin 36 which is fixedly arranged on the heating device 2 actuates aswitch 11 which corresponds to this heating device, and, consequently, aheating program of a program control 12 which is fixed for thisdimension is adjusted. The program control 12 is arranged in the frame 1and is operatively connected to a control panel, not shown, arranged atthe front.

An electrically driveable small compressor 14 (schematically illustratedin FIG. 1) is additionally arranged in frame 1. The small compressor 14is provided for generating compressed air for an expandable supportdevice 15. The support device 15 is constructed as a bladder and isconnected to the compressor by means of an air line 16. A pressuresensor 17 arranged in the air line 16 is operatively connected to theprogram control through a pressure adjusting device and ensures that thenecessary pressure is maintained in the bladder during the weldingprocedure. The compressor is automatically switched on when the pressuredrops.

Each pipe clamping device 3 has an upper portion 41 which is fastened toa lower portion 40 by means of a hinged joint 23 so that the upperportion 41 can be pulled up. Replaceable, half shell-shaped clampingjaws 42 are arranged in both portions. The clamping jaws 42 appropriatefor each diameter dimension to be welded are then inserted and fastenedin the lower portion 40 and the upper portion 41. The clamping device 24for clamping together the lower portion 40 and the upper portion 41 isof the same construction as the clamping device in the heating device 2.

The electric heating cartridges 33 in the heating devices 2 each have athermal sensor 37 and are operatively connected to program control 12.

The program control has an adjusting element corresponding to eachelectric switch 11 for adjusting a certain heating power

The heating power is determined by integrating the measured temperatureat the heating device over time. The integration begins at an adjustabletemperature, such as, for example, 210° C.

FIGS. 4 and 5 show an embodiment of the heating device 2 which can alsobe mounted on a frame 1 and can be connected to the frame 1 in adetermined position by means of a pin 51 and a gripping device 50. Aplug component 52 which includes plug contact 53 is arranged in thehousing 20a of the lower portion 20.

A second plug component 54 with plug contact 55 which corresponds to theplug contact 5 is inserted in the plug component 52 with simultaneouscentering on pin 51 after the heating device 2 has been mounted. Each ofthe plug components 52, 54 have preferably fifteen plug contacts 53 or55, wherein always four are provided for the two heating cartridges 33and four for the two thermal sensors 37. The connection of the contactscan be effected with the program control 12. Seven plug contacts areprovided for coding the different heating devices 2 which are requiredfor the different diameter dimensions. As a result, the welding programis activated in the program control 12 which is required for therespective diameter dimension. These plug contacts replace the electricswitch 11 and the pin 36 described in connection with FIGS. 1 to 3, sothat the device is simplified.

A holding component 60 each is fastened in the lower portion 20 and theupper portion 22 of the heating device 2. A heating jaw 62 each isarranged centered in a recess 61 of the holding component 60.

The heating jaw 62 has in the middle portion 63 a thin wall thicknesstoward the receiving means 21 because of a recess 64, so that a goodheat passage is provided from the heating cartridge to the weldingpoints.

A heating component 65 preferably of copper is arranged in the recess 64and is fixedly connected by soldering to the heating jaw 6 which is ofstainless steel. The heating cartridge 33 and the thermal sensor 37 arearranged inserted in the heating component 65. The temperature patterncan be determined in the middle portion 63 o the so-called heating zoneby the shape of the recess 64 in the cross-section thereof. The portions66 on both sides, which are the tempered zones, are less heated becausethey have a greater wall thickness D.

Recesses 67 are arranged on the outer circumference of the holdingcomponent 60. The recesses 67 form the duct 34 for conducting thecooling air generated by the ventilator 9.

A recess 68 is arranged on the inner circumference of the holdingcomponent 60 and in the middle with respect to the receiving means ofthe heating component 65. Cooling air is also conducted through therecess 68 for a quick cooling of the heating component 65 and, thus, ofthe welded connection.

This embodiment is otherwise constructed in the same manner as thedevice described with respect to FIGS. 1-3.

The welding procedure is carried out as described below.

The heating device 2 corresponding to the diameter dimension of thepipes or fittings to be welded is placed on the guides 4 and thecorresponding clamping jaws 42 are inserted in the pipe clamping devices3.

Pipes and fittings are mounted in the heating device and, in the case ofpipes, in the pipe clamping device and are fixedly clamped by clampingthe lower portion 22 or 41 against the lower portion 20 or 40 by meansof the clamping devices 24.

By mounting the heating device 2, the corresponding welding parametersare automatically adjusted by switching of the corresponding electricswitch 11 or by the plug contacts 53, 55. When the pipes or fittings aremounted, the bladder 15 is arranged in the interior in the region of thewelded connection. By pressing the "start" key, the following sequenceis automatically released:

1. The bladder is pressurized by switching on the compressor.

2. The heating is switched on, wherein the adjusted maximum temperature(200° to 300° C.) is quickly reached without overshooting. The heatingenergy required for each dimension was adjusted prior to the weldingprocedure. The heating energy integration begins at approximately 210°C.

3. The heating is switched off after the adjusted heating energy hasbeen reached.

4. The cooling air ventilator is switched on until and adjustabletemperature of approximately 90° C. has been reached.

5. The supply of cooling air is switched off. Simultaneously, thepressure is relieved from the bladder.

6. The welding procedure is concluded. The welded pipes or fittings areremoved from the device and the bladder is pulled out.

The device is ready for manufacturing the next welded connection.

We claim:
 1. A device for manufacturing a welded connection of tubularcomponents of plastics material, the tubular components having ends,wherein the ends of the components to be connected are axially alignedand held to abut with end surfaces thereof, and wherein the ends of thetubular components can be heated by means of a foldable heating devicewhich surrounds the tubular components, the device comprising a supportdevice arranged in the interior of the tubular components, a heatingdevice (2) which can be fastened on frame (1) in a determined positionbeing provided for each pipe diameter dimension to be welded, electricalcontacts (53, 55, 11) being provided for each heating device (2) meansfor selecting a welding program of a program control (12) predeterminedfor each dimension by means of the contacts (53, 55, 11) when theheating device (1) is placed on the frame, a changeable heat energysupply which is adjustable over time being provided for each weldingprogram, the heating device (2) including electrically heatable jaws(28, 62) and electric heating cartridges (33) for heating the heatingjaws (28), the heating jaws (28) having thermal sensors (37) which areoperatively connected to the program control (12), wherein theelectrical contacts (53, 55) are arranged in a first plug component (54)arranged on the frame (1) and on a second plug component (52) arrangedin the heating devices (2), wherein the electrically heatable jaws (28,62) are surrounded by a common duct (34) which is operatively connectedto a ventilator (9) which produces cooling air, the ventilator (9) beingarranged in the frame (1) directly underneath the heating device (2),and wherein the heating jaws (62) have in a middle portion (63) thereofa thin wall thickness compared to adjacent portions (66) thereof locatedon both sides of the middle portion.
 2. The device according to claim 1,wherein the frame (1) has longitudinal guides (4) on which the heatingdevice can be fastened in a determined position and wherein at least onefoldable pipe clamping device (3) with clamping jaws (42) can be grippedin a position which is adjustable in longitudinal direction.
 3. Thedevice according to claim 1, wherein an electrically driveablecompressor (14) is arranged in the frame (1) for generating compressedair.
 4. The device according to claim 3, wherein the compressor (14) isconnected by means of an air line (16) to a support device (15) which isconstructed as a bladder and can be expanded by compressed air.
 5. Thedevice according to claim 1, wherein each heating jaw (62) is fixedlyconnected in the middle portion (63) with a heating component (65) whichis of copper and includes the heating cartridge (33), and that theheating jaw (62) is of stainless steel.